Bayer has long denied that its birth control pills, Yaz and Yasmin, put women at greater risk for life threatening blood clots, but a new study published in the British Medical Journal says the “fourth generation” oral contraceptives, which contain the progestin drospirenone, put women at twice the risk for blood clots than those that contain the hormone levonorgestrel.
Levonorgestrel is a progestogen that is used in both combination hormone pills and progestogen-only formulations. It is known by the brand names Escapelle, Plan B, Levonelle, NorLevo, Postinor-2, i-pill, Next Choice, and 72-HOURS. It is also the active ingredient in the Mirena-brand intrauterine device (IUD).
Blood clots have always been a risk factor with birth control pills, but mounting lawsuits against Bayer argue that Bayer’s formulation of drospirenone and ethinyl estradiol in Yaz and Yasmin puts women at greater risk. The same formulation of hormones is also in the generic oral contraceptive Ocella, as well as Bayer’s newly introduced folic acid-fortified pills Bayaz and Safyral.
Researchers from the Boston Collaborative Drug Surveillance Program at Boston University School of Medicine studied about 900 women on birth control since 2002. The blood clot risk for women taking Yaz or Yasmin was 30.8 per 100,000 person-years. Women on pills containing levonorgestrel had a rate of only 12.5 per 100,000 person-years.
Most alarming, researchers also found that women younger than 30 who used Yaz or Yasmin were at even greater risk for blood clots than women on second-generation pills. These young women had an incidence rate of 24.8 per 100,000 compared to only 5.39 per 100,000 if they took pills containing levonorgestrel.